Wireless communication systems that utilize radio frequency carriers are well known in the art. Such systems include cellular telephone services and trunked dispatch services. Dispatch services differ from telephone services in a variety of ways, but are perhaps most easily distinguished from one another in that telephone communications are typically between two individuals that are uniquely and individually identified within the system, whereas dispatch communications allow for communications amongst a group of users, without the need to individually identify each group member before initiating the communication.
Both of these services are typically offered in most populated areas. The telephone services as provided through cellular systems are utilized by those who wish to have person-to-person access through the existing telephone network, and dispatch services are typically utilized by organizations, such as public safety agencies and various business operations, that require communications within groups of mobile users. Traditionally these two services have been offered separately, because of the different nature of communications. Recently, however, there have been communications systems designed offering both services. These are the so-called integrated services radio systems. Integrated services radio systems allow communications between individuals over the public switched telephone network, and dispatch type communications among groups of mobile users.
These systems take advantage of the similarities of such systems, and offer a competitive advantage since the cost of infrastructure equipment is reduced compared to outfitting separate telephone and dispatch systems. Such systems reduce the number and need for suitable antenna sites, for example, as well as base station facilities. Further benefiting the user, the user equipment, often hand held radio devices, offer access to both services, therefore reducing the burden on the user by eliminating the need to carry multiple devices. As a result, such systems are gaining widespread marketplace acceptance.
In using an integrated services radio communications system, there may arise a conflict between services when, for example, a user is involved in telephone call, and receives dispatch message for a group to which the same user belongs, or if the user needs to initiate a dispatch call. To date, in order to respond to the dispatch message or initiate one, the user must end the telephone call before proceeding with any other communications activity. This is obviously inconvenient to the user. Therefore, there is a need, in an integrated services radio system, for a means by which a user can respond to a dispatch message, while retaining telephone service.